If you think your too deep into the friend trap man up your way out of it. What I mean is this: When your stuck in that category they see you as something sexless. You might as well be one of her girlfriends. What you need tgo do is remind her that you're a man. Be corageous, protective, gentlemanly, self-assured domineering, all the things a man should be. That will tingle her hormones and raise your alpha male profile. Take off your shirt and show off your pecs if you have to damn it!
Remember you're a man and she's a woman, and you can't cheat nature. The problem is that when we become friends we tend to tone down our manliness. You need to reverse that tendency - be a man and trat her like a woman. Put you arm around her, give her a kiss, defend her from an evil wronngdoer. Give her a teaser of what she's missing for not being your girl.